Wire for inserting into biological duct

ABSTRACT

A wire for insertion into intravital tracts applicable even to small-diameter tracts while securing the stream in the tract is to be provided. A capture filter  2  is disposed at the tip of a principal wire  1  consisting of steel filaments. The capture filter  2  is configured of four support wires  3  and a basket-shaped filter body  4  consisting of a meshed material. The filaments constituting the support wires  3  and those constituting the filter body  4  are integrally formed and consist of a superelastic alloy.

TECHNICAL FIELD

The present invention relates to a wire for insertion into intravitaltracts provided with a capture filter to be temporarily arranged in anintravital tract, such as a blood vessel, to capture embolic material orthe like in the tract.

BACKGROUND ART

In many cases of treating a lesion in an intravital tract, such asremoving cholesterol or anything else that has accumulated in a bloodvessel or removing gallstones in the gall duct, the substance concernedis removed from the wall surface of the tract. Where a blood vessel isto be so treated, these pieces of the removed substance will be carriedby the blood flow and may block thinner blood vessels downstream.

According to a technique to address this problem disclosed inJP2001-212152A (hereinafter referred to as Patent Reference 1), a filteris temporarily arranged in the tract by inserting a wire provided with acapture filter, and such potentially embolic material is captured by thefilter.

The capture filter according to Patent Reference 1 comprises a cage bodycomposed by joining three or more linear alloy wires with one another atboth front and rear ends and swelling midway parts of the plurality ofalloy wires in the radial direction to arrange them along asubstantially football-shaped border face, and an umbrella-shaped coveris formed by covering with an elastic membrane the part of the outersurface of that cage body, for instance, from the front end tosubstantially the middle point; embolic material is captured by thatumbrella-shaped cover.

The wire is inserted into a leading catheter, and the capture filter ina state of being kept folded is inserted together with the leadingcatheter into a blood vessel. When they reach the target region, thefront end of the wire is fed out forward from the leading catheter tolet out the capture filter from the leading catheter into theaforementioned shape of swelling in the radial direction.

However, in the wire for insertion into intravital tracts, as theumbrella-shaped cover consisting of a membrane constitute the filter tocapture embolic material, there is a fear that the umbrella-shaped coveritself may obstruct blood circulation in the blood vessel. There is aversion in which many holes are bored in that membrane, but this stillinvolves a fear of failure to ensure a sufficient blood stream.

Further, to consider a state in which capture filter is folded, thediameter of the capture filter will be increased by the thickness of themembrane doubled by the folding, and the filter will becomecorrespondingly less adaptive to thin tracts.

An object of the present invention, attempted in view of these problems,is to provide a wire for insertion into intravital tracts whose diametercan be reduced without sacrificing the smoothness of the stream withinthe tract.

DISCLOSURE OF THE INVENTION

In order to solve the problems noted above, a wire for insertion intointravital tracts according to the aspect of the present inventionstated in claim 1 uses as a principal wire flexible filaments to beinserted into an intravital tract, the tip of that principal wire beingprovided with a capture filter, the wire for insertion into intravitaltracts being characterized in that the capture filter comprises a filterbody consisting of a plurality of support wires all of whose nearer endsare spliced to the principal wire and radially extending in thedirection toward the farther end and in the direction toward the outerdiameter and a meshed material linked to the plurality of support wiresand knit in such a shape that the face toward the support wires form aconcave, and the filaments constituting the plurality of support wiresand filter body have an elastic force to form the shape.

According to the invention, by configuring the filter body of a meshedmaterial, obstruction of the stream within the intravital tract isavoided.

Also, since it can be folded correspondingly smaller to the absence ofthe membrane unlike in the conventional one, it can be applied to tractsthinner in diameter.

Furthermore, the presence of the elastic force to form theaforementioned shape, no other mechanism to achieve swelling into theintended shape is needed, and the configuration is correspondinglysimplified to make possible more compact folding.

Next, according to the aspect of the invention stated in claim 2, in theconfiguration stated in claim 1, the mesh size of the meshed materialdecreases toward the central part of the concave, which is the fartherend direction.

Since the stream of fluid in a tract is the highest in flow rate in thecentral part of the tract, embolic material floating in the fluid iscaptured, first from the concave central position of the filter bodyconsisting of a meshed material. Therefore, by setting the meshes of theconcave central position of the filter body smaller than anywhere elseas according to the invention under the present application, the streamof the fluid can be more easily ensured by the meshes of the outercircumference of the filter while securely capturing small pieces ofembolic material.

Since the meshes of the meshed material here are so inclined as toflatly lie relative to the stream of the fluid, more so toward the outercircumference whether the mesh openings are larger in relative terms,the aperture is equal to finer meshes in relative terms in a sectionalview orthogonal to the stream of the fluid.

Next, according to the aspect of the invention stated in claim 3, in theconfiguration stated in claim 1 or claim 2, the filaments constitutingthe plurality of support wires and filter body consist of a shape-memoryalloy.

The composition using a shape-memory alloy makes more securerestorability of the originally intended shape even after staying in afolded state for a long time.

More preferably, it should be a superelastic alloy out of shape-memoryalloys.

Next, according to the aspect of the invention stated in claim 4, in theconfiguration stated in any one of claim 1 through claim 3, the ends ofthe plurality of filaments knitted into a mesh form to constitute thefilter body are divided into a plurality of sets, and the ends offilaments of each set are twined to form each of the support wires.

According to the invention, filaments constituting the support wires andfilaments constituting the filter body are integrated to dispenseprocessing to separately join the support wires and the filter body,with the result that no swollen nodal part is formed in any of thejoined portions, making possible folding to a correspondingly thinnerdiameter.

Next, according to the aspect of the invention stated in claim 5, in theconfiguration stated in any one of claim 1 through claim 4, there isprovided with a guide wire joined to the convex side of the filter bodyand extending in the farther end direction.

The presence of the guide wire facilitates guidance of the capturefilter swelling in the radial direction along the intravital tract.

Incidentally, it is preferable for the guide wire to be more flexible inthe radial direction than the principal wire. While the principal wireis required to be just sufficiently rigid to permit feeding in the axialdirection, it is preferable for the guide wire to have flexibility topermit trackability in the extending direction of the tract.

Next, according to the aspect of the invention stated in claim 6, in theconfiguration stated in claim 5, the central part of said filter body isjoined to the nearer end side of a first tubular piece and fixed to thefirst tubular piece in a state in which the nearer end of said guidewire is inserted into the farther side of that first tubular piece.

Next, according to the aspect of the invention stated in claim 7, in theconfiguration stated in any one of claim 1 through claim 6, the nearerends of the plurality of support wires are all fixed to a second tubularpiece in a state in which they are inserted into the farther side of thesecond tubular piece, and fixed to the second tubular piece in a statein which the tip of the principal wire is inserted into the nearer sideof said second tubular piece.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a drawing showing a wire for insertion into intravital tractspertaining to a mode for carrying out the present invention.

FIG. 2 is a drawing for describing an example fabrication of a capturefilter pertaining to a mode for carrying out the invention.

FIG. 3 is a drawing representing data of an embodiment.

BEST MODES FOR CARRYING OUT THE INVENTION

The present invention will be described in more detail with reference tothe accompanying drawings.

FIG. 1 is a drawing showing a wire for insertion into intravital tractsin this mode for implementation and the state of its use. This FIG. 1 isa drawing of a state of insertion into a lesioned position in a bloodvessel, which is one of intravital tracts.

As shown in FIG. 1, a capture filter 2 is disposed at the tip of aprincipal wire 1 consisting of steel filaments.

The capture filter 2 is configured of four support wires 3 and abasket-shaped filter body 4 consisting of a meshed material, concavetoward the nearer position (convex toward the farther position).

The four support wires 3 are joined into one by twining their respectivenearer ends 3 a together. In this mode for implementation, the joiningis accomplished by inserting the nearer ends 3 a of the four supportwires 3 from the farther side in a second tubular piece 6 and fixingthem within the second tubular piece 6 by welding, swaging or otherwise.

And each of the four support wires 3 extends radially toward the fartherside and in the direction of the outer diameter.

Further, the filter body 4 consisting of the meshed material is formedinto a meshed state by twining many filaments and into a basket shapewhose face toward the nearer side is concave. Incidentally, it is notconfined to a basket shape if the nearer side (the support wires 3 sideor the principal wire 1 side) is concave and can capture embolicmaterial. It is preferable, though, for the meshes of meshed material tobecome finer toward the central part of the concave.

The central convex side part (farther side part) of that filter body 4is inserted into the nearer side part of a first tubular piece 5, andfixed within the first tubular piece 5 by welding, swaging or otherwise.

Further, the farther side ends of the four support wires 3 are madecontinuous from the nearer side end of the filter body 4 to integratethe four support wires 3 and the filter body 4.

And the tip of the principal wire 1 is inserted from the nearer side ofthe second tubular piece 6 and fixed to the second tubular piece 6.

Also, a guide wire 7 is inserted from the farther side of the firsttubular piece 5 and fixed to the first tubular piece 5. Although thisguide wire 7 also consists of steel filaments, it is more flexible inthe radial direction than the principal wire 1. For this reason, even ifthe blood vessel is meandering, it can adequately guide the capturefilter 2 along the blood vessel.

The filaments constituting the support wires 3 and the filter body 4which make up the capture filter 2 in this mode for implementationconsist of a superelastic alloy, which is a type of shape-memory alloy;by confining them in the aforementioned intended shape and subjectingthem to heat treatment, for instance, at 500° C. for 40 minutes, theyare caused to memorize that shape.

By being composed of such a super elastic alloy, the capture filter 2 isprovided with an elastic force to form the shape.

Further in this mode for implementation, generation of a swelled part inthe nodal portion between the support wires 3 and the filter body 4 isaverted by integrating the filaments constituting the four support wires3 and those constituting the filter body 4.

To show an example of fabrication of the capture filter 2 by integratingthe filaments constituting the four support wires 3 and thoseconstituting the filter body 4 as stated above, a mesh is formed by sotwining such filaments that 36 filaments 2 a be arranged vertically and36 filaments 2 b arranged laterally as shown in FIG. 2 for instance; thecentral part A of the mesh is pulled backward as viewed in the drawingto form a basket-shaped concave to configure the filter body 4; and atthe same time the respective ends of the four-filament sets (the partdenoted by reference sign B in FIG. 2) are twined together to form thesupport wires 3.

Here, by pulling the central part A of the mesh to form the basketshape, a state in which the meshes are the finest in the central part ofthe concave, i.e. a state in which the meshes become finer as theyapproach the central part of the concave, is achieved.

Of course, the method of integrally fabricating the filamentsconstituting the four support wires 3 and those constituting the filterbody 4 is not limited to this. For example, the concave of the filterbody 4 can be formed by knitting filaments in a pipe shape as if to makea stocking, closing one of the open ends; at the same time the supportwires 3 can be formed by dividing the filaments positioned at the otheropen end into sets of two each and twining them together. In this case,too, a meshed material whose meshes are the finest in the central partof the concave can be obtained by pulling one open end when it is to beclosed.

To add, though it is preferable for the number of the support wires 3 tobe three or more, two could also be acceptable.

Next, an example of use of the wire for intravital insertion will bedescribed.

The wire for intravital insertion is inserted into a leading catheter 10and, the state of the filter body 4 being held in the leading catheter10 being kept as it is, the leading catheter 10 is injected into a bloodvessel 11, which is a tract, and the tip of the leading catheter 10 ismoved to the target position in the blood vessel, i.e. a lesionedposition 12 (e.g. a stenosis region).

The filter body 4 here, in the state it is held in the leading catheter10, is confined by the inner circumferential face of the leadingcatheter 10 to be folded to the size of the bore of the leading catheter10.

Next, the filter body 4 is placed in the blood stream by so manipulatingthe principal wire 1 as to force the filter body 4 of the wire forinsertion into intravital tracts out of the tip of the leading catheter10 in the direction of the farther side (see FIG. 1). The filter body 4,once out of the leading catheter 10, is no longer confined by theleading catheter 10, swells out in the radial direction to automaticallyreturn to its original shape.

Next, after retreating the leading catheter 10 to before the stenosisregion, the principal wire 1 is pulled back while applying a rotatingaction to the principal wire 1, and accumulated matter having built upin the blood vessel is scrapped off with the support wires 3. Thescraped-off accumulated matter is collected into the concave of thefilter body 4.

Then, upon completion of the collection, the leading catheter 10 and thefilter body 4 are returned to inside a guide catheter not shown, and allof them are retreated in a state of being held in the guide catheter.

Incidentally, accumulated matter may as well be scraped off with anothertool.

In the wire for insertion into intravital tracts, since the filter body4 is configured of a mesh formed by twining filaments, the blood streamcan be sufficiently ensured.

Herein, whereas the meshes of the filter body are the finest in thecentral part of the concave and more coarse toward the outercircumference, this gives a structure in which capturing begins in thecentral part of the concave and smooth flowing of the blood stream isfacilitated by the coarse meshes toward the outer circumference, becausethe blood stream is the fastest in the central part of the blood vessel.Also, even if the mesh openings on the outer circumference side aresomewhat greater in size than the target accumulated matter, therelative mesh openings in relative terms as viewed on a sectionorthogonal to the blood stream are fine enough to make capturingpossible because scraping-off begins in the central part of the concavewhere the meshes are fine as stated above and the meshes areincreasingly inclined toward the outer circumference in a lying posturerelative to the blood current.

Also, by configuring the filaments of a superelastic alloy, they areenabled to automatically return to their original shape by merelydrawing them out of the leading catheter 10, and therefore no separatemechanism is needed to cause the filter body 4 to swell out in theradial direction, and the capture filter 2 is enabled to be folded to acorrespondingly smaller diameter.

Further, since the support wires 3 and the filter body 4 in a mesh stateare configured of integrated filaments to allow no swollen modal portionto be formed on the boundary between the support wires 3 and the filterbody 4, the capture filter 2 is thereby enabled to be folded to acorrespondingly smaller diameter.

As a result, it is made possible to insert the wire into a thinner bloodvessel than a conventional such device can, and lesions in such thinblood vessels can be coped with.

Also, by disposing the more flexible guide wire 7 than the principalwire 1 on the farther side of the capture filter 2, the capture filter 2is enabled to smoothly move, guided by the guide wire 7, even in ameandering blood vessel. The greater flexibility of the guide wire 7than the principal wire 1 is intended to prevent the blood vessel wallfrom being damaged. The guide wire 7 can be dispensed with, though.

Also, by fixing the capture filter 2 to the principal wire 1 via thesecond tubular piece 6, splicing of the principal wire 1 to the capturefilter 2 is facilitated.

Splicing between the capture filter 2 and the guide wire 7 is alsofacilitated by the intervening of the first tubular piece 5.

Although a case of configuring the support wires 3 and the filter body 4of integrated filaments is illustrated here regarding the abovedescribed mode for implementation, it is also permissible to configurethe support wires 3 and the filter body 4 of separate filaments andsplicing the farther ends of the support wires 3 and the filter body 4by welding or otherwise. However, the folded diameter will becomethicker than in the foregoing embodiment by the thickness of the nodalportion, making the fabrication for manufacturing more troublesome. Toadd, if the linking positions between the individual support wires 3 andthe filter body 4 are lagged in the axial direction of the principalwire 1 to prevent the nodal portions overlapping one another, thediameter can be set correspondingly smaller.

Also, though a case of configuring the filaments constituting thecapture filter 2 of a superelastic alloy is illustrated here regardingthe above described mode for implementation, they may also be composedof a shape-memory alloy which makes the temperature in the lesionedtract a transformation temperature. However, the use of a superelasticalloy makes the restoration of the original shape more certain when thefilter is taken out of the leading catheter 10. Incidentally, ashape-memory resin may as well be used in place of a shape-memory alloy.

To add, it is not necessary to use a shape-memory alloy for all thefilaments constituting the filter body 4, but some of the filamentswhich are twined may consist of another material. Even in this case, theshape-memory alloy part would exert elasticity to restore the originalshape.

Also, the material for the filaments to constitute the capture filter 2is not limited to a shape-memory alloy. For instance, they may be formedof a metal material, such as steel, and fabricated to provide elasticityof urging them in the direction of the intended shape. It is preferablefor them to be formed of the shape-memory alloy, though, because theymay not be restored when taken out of after a state of insertion in theleading catheter 10 for a long period.

Further, though the foregoing description referred to the blood vessel11 as an example of intravital tract, the object is not limited to theblood vessel 11, but application to another intravital tract, such asthe gall duct, is also possible. The invention excels in itsapplicability to small-diameter intravital tracts, though.

EMBODIMENT

An embodiment was configured of a capture filter 2 having a maximumexpansible diameter of 8 mm and a filter body 4 consisting of 72filaments. In this case, the diameter and mesh size of the expandedfilter body 4 theoretically has a relationship shown in FIG. 3. The meshopening sizes in the drawing are given in terms of diameters in theopening sectional areas converted into circular areas.

And a wire for intravital insertion equipped with the capture filter wasarranged in a glass tube of 5.8 mm in bore, instead of a blood vessel,and a capture experiment was carried out. Incidentally, the maximum meshsize in this experiment was 0.25 mm.

And, while circulating water in the glass tube at a flow rate equivalentto the blood stream, polyvinyl alcohol (PVA) of 100 to 200 micrometersin grain size was let flow, and the weight of the PVA particles whichwere not captured and passed the filter was measured for evaluation.

As a result of the evaluation, it was confirmed that the capture filterhad succeeded in capturing 95% of PVA. Thus, it is seen that sufficientcapturing can be accomplished even if the meshes on the outercircumference are greater than the object to be captured.

INDUSTRIAL APPLICABILITY

As hitherto described, the wire for insertion into intravital tractsaccording to the present invention not only makes it possible to scrapeoff embolic material and the like while securing circulation within atract, but also enables insertion into a tract of a thinner diameter,thereby enabling lesions in such thinner tracts to be treated.

1. A wire for insertion into intravital tracts using as a principal wireflexible filaments to be inserted into an intravital tract, the tip ofthat principal wire being provided with a capture filter, the wire forinsertion into intravital tracts being characterized in that the capturefilter comprises a filter body consisting of a plurality of supportwires all of whose nearer ends are spliced to the principal wire andradially extending in the direction toward the farther end and in thedirection toward the outer diameter and a meshed material linked to theplurality of support wires and knit in such a shape that the face towardthe support wires form a concave, the ends of the plurality of filamentsknitted into a mesh form to constitute the filter body are divded into aplurality of sets, and the ends of filaments of each set are twined toform each of the support wires, and the filaments constituting theplurality of support wires and filter body have an elastic force to formthe shape.
 2. The wire for insertion into intravital tracts according toclaim 1, characterized in that: the mesh size of the meshed materialdecreases toward the central part of the concave, which is the fartherend direction.
 3. The wire for insertion into intravital tractsaccording to claim 1, characterized in that: The filaments constitutingthe plurality of support wires and filter body consist of a shape-memoryalloy.
 4. (canceled)
 5. The wire for insertion into intravital tractsaccording claim 1, characterized in that: it is provided with a guidewire joined to the convex side of the filter body and extending in thefarther end direction.
 6. The wire for insertion into intravital tractsaccording to claim 5, characterized in that: the central part of thefilter body is joined to the nearer end side of a first tubular pieceand fixed to the first tubular piece in a state in which the nearer endof the guide wire is inserted into the farther side of that firsttubular piece.
 7. The wire for insertion into intravital tractsaccording to any one of claim 1, characterized in that: the nearer endsof the plurality of support wires are all fixed to a second tubularpiece in a state in which they are inserted into the farther side of thesecond tubular piece, and fixed to the second tubular piece in a statein which the tip if the principal wire is inserted into the nearer sideof the second tubular piece.